text: /*
   * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License").
   * You may not use this file except in compliance with the License.
   * A copy of the License is located at
   *
   *  http://aws.amazon.com/apache2.0
   *
   * or in the "license" file accompanying this file. This file is distributed
   * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
   * express or implied. See the License for the specific language governing
   * permissions and limitations under the License.
   */
  
  #include <sys/param.h>
  #include <stdint.h>
  
  #include "tls/extensions/s2n_client_alpn.h"
  
  #include "tls/extensions/s2n_extension_type.h"
  #include "tls/s2n_protocol_preferences.h"
  #include "tls/s2n_tls.h"
  #include "tls/s2n_tls_parameters.h"
  
  #include "utils/s2n_safety.h"
  
  static bool s2n_client_alpn_should_send(struct s2n_connection *conn);
  static int s2n_client_alpn_send(struct s2n_connection *conn, struct s2n_stuffer *out);
  static int s2n_client_alpn_recv(struct s2n_connection *conn, struct s2n_stuffer *extension);
  
  const s2n_extension_type s2n_client_alpn_extension = {
      .iana_value = TLS_EXTENSION_ALPN,
      .is_response = false,
      .send = s2n_client_alpn_send,
      .recv = s2n_client_alpn_recv,
      .should_send = s2n_client_alpn_should_send,
      .if_missing = s2n_extension_noop_if_missing,
  };
  
  static bool s2n_client_alpn_should_send(struct s2n_connection *conn)
  {
      struct s2n_blob *client_app_protocols;
  
      return s2n_connection_get_protocol_preferences(conn, &client_app_protocols) == S2N_SUCCESS
              && client_app_protocols->size != 0 && client_app_protocols->data != NULL;
  }
  
  static int s2n_client_alpn_send(struct s2n_connection *conn, struct s2n_stuffer *out)
  {
      struct s2n_blob *client_app_protocols;
      POSIX_GUARD(s2n_connection_get_protocol_preferences(conn, &client_app_protocols));
      POSIX_ENSURE_REF(client_app_protocols);
  
      POSIX_GUARD(s2n_stuffer_write_uint16(out, client_app_protocols->size));
      POSIX_GUARD(s2n_stuffer_write(out, client_app_protocols));
  
      return S2N_SUCCESS;
  }
  
  static int s2n_client_alpn_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
  {
      uint16_t size_of_all;
      struct s2n_stuffer server_protos = {0};
  
      struct s2n_blob *server_app_protocols;
      POSIX_GUARD(s2n_connection_get_protocol_preferences(conn, &server_app_protocols));
  
      if (!server_app_protocols->size) {
          /* No protocols configured, nothing to do */
          return S2N_SUCCESS;
      }
  
      POSIX_GUARD(s2n_stuffer_read_uint16(extension, &size_of_all));
      if (size_of_all > s2n_stuffer_data_available(extension) || size_of_all < 3) {
          /* Malformed length, ignore the extension */
          return S2N_SUCCESS;
      }
  
      struct s2n_blob client_app_protocols = { 0 };
      client_app_protocols.size = size_of_all;
      client_app_protocols.data = s2n_stuffer_raw_read(extension, size_of_all);
      POSIX_ENSURE_REF(client_app_protocols.data);
  
      /* Find a matching protocol */
      POSIX_GUARD(s2n_stuffer_init(&server_protos, server_app_protocols));
      POSIX_GUARD(s2n_stuffer_skip_write(&server_protos, server_app_protocols->size));
  
      while (s2n_stuffer_data_available(&server_protos) > 0) {
          struct s2n_blob server_protocol = { 0 };
          POSIX_ENSURE(s2n_result_is_ok(s2n_protocol_preferences_read(&server_protos, &server_protocol)),
                  S2N_ERR_BAD_MESSAGE);
  
          bool is_match = false;
          POSIX_ENSURE(s2n_result_is_ok(s2n_protocol_preferences_contain(&client_app_protocols, &server_protocol, &is_match)),
                  S2N_ERR_BAD_MESSAGE);
  
          if (is_match) {
              POSIX_CHECKED_MEMCPY(conn->application_protocol, server_protocol.data, server_protocol.size);
              conn->application_protocol[server_protocol.size] = '\0';
              return S2N_SUCCESS;
          }
      }
      return S2N_SUCCESS;
  }
  
  /* Old-style extension functions -- remove after extensions refactor is complete */
  
  int s2n_extensions_client_alpn_send(struct s2n_connection *conn, struct s2n_stuffer *out)
  {
      return s2n_extension_send(&s2n_client_alpn_extension, conn, out);
  }
  
  int s2n_recv_client_alpn(struct s2n_connection *conn, struct s2n_stuffer *extension)
  {
      return s2n_extension_recv(&s2n_client_alpn_extension, conn, extension);
  }
  